Factual error: In the beginning of the anime sequence we see O-Ren's father from behind, along with his Army rank on his left shoulder. The rank in the movie has two chevrons on top (the upside down "V"s), three "rockers" on the bottom (the bowl shapes) and a star in the middle. The real Army rank of Sergeant Major has three chevrons on top - no rank except corporal has only two chevrons, and corporals have no rockers or other insignia.
Factual error: Near the end of the anime sequence when O-Ren murders the crime boss, there's a shot of the wall/ceiling behind her as she pulls the sword out of his stomach and you see the outline of O-Ren in the blood on the wall. In the next shot of O-Ren's face and body she only has minimal amounts of blood on her. Considering there was enough blood spraying out that you can see her outline on the wall behind her, shouldn't the front of her be covered in the blood as well?